Construction material made of algae and method for producing thereof

ABSTRACT

The present disclosure describes use of filamentous algae to form insulating construction materials which provide thermal and noise insulation. Algae from the order Zygnematales, the Cladophorales, or the Ulotrichales can be dried and formed for use as insulating material. Algae mass can be combined into several layers, using a binder to attach the layers to each other. A composite material of algae mass and an additive can be used and form the body of insulation panels having honeycomb-shaped chambers, which are sealed by a foil that is laminated onto the body.

TECHNICAL FIELD

The present disclosure relates to construction materials made of algaeand methods and plants for production thereof.

BACKGROUND

Algae are known to be used as fertilizer, as food, and as a pollutioncontrol in sewer plants. Recently, their ability to produce more biomassper unit area in a year than any other form of biomass has increasedinterest in algae as a renewable energy source. Cultivating algae forthis purpose usually involves algae species that can produce algae oiland requires closed containers, a tightly controlled environment, andsophisticated process technology. Chlorella, a genus of single-celledgreen algae, has been used for fuel production. The presence of otheralgae, especially fast growing hair algae, is undesirable in such algaefuel plants.

Some algae, e.g. those of the Cladophora, have been used in fireretardant building material known in German as “Algilit”. “Algilit” isknown to having been used in western Siberia for many years. Algalplastics which comprise a foamed and stabilized filamentous algal fibermatrix having substantial dimensional stability are disclosed in U.S.Pat. No. 5,779,960.

Carbon dioxide is considered a green house gas, increasing concentrationof which in the earth's atmosphere leads to a rise in global temperaturelevels, an effect often referred to as global warming. A reduction incarbon dioxide emissions is deemed desirable. Ideally, the concentrationof carbon dioxide in the atmosphere would be kept constant or evenreduced, by permanently withdrawing carbon dioxide from the atmosphereat the same or at a faster rate than carbon dioxide is emitted into theatmosphere. However, reducing or eliminating the emission of carbondioxide that is generated by fossil fuel power plants such as coal, oilor gas power plants, has proven to be difficult, inefficient, andexpensive. The ability to reduce carbon dioxide emissions is however ofparticular interest in jurisdictions that regulate carbon dioxideemissions, including taxing such emissions, for example by requiring anemitter to purchase carbon dioxide emission rights.

One approach to reducing carbon dioxide emissions from fossil fuel powerplants is to pump carbon dioxide that is generated in power plants intounderground storage, e.g. caverns or retired mines. However, thisapproach is expensive and potentially dangerous, if carbon dioxideescapes from its underground storage.

Another approach is to switch power generation plants from fossil fuelsto renewable fuels, thereby reducing the dependency on coal, oil and gasas energy sources. However, renewable energy sources from crop competewith crop needed as food, are inefficient, and can at best case becarbon neutral. Burning renewable energy typically emits about the sameamount of carbon dioxide that the underlying crop has withdrawn from theatmosphere during its growth. A reduction of the carbon dioxide in theatmosphere is not possible.

SUMMARY

The present disclosure reveals a new use for filamentous algae which areproduced in cultivation pools filled with pre-treated waste water andinto which carbon dioxide is injected to create insulating constructionmaterials. It has been found, that dried algae mass can be used to formconstruction material, especially thermal and noise insulation material.The filamentous algae used in construction material bind carbon dioxide,permanently removing it from the earth's atmosphere. Constructionmaterial comprising filamentous algae is hence eligible to receivecredits for carbon dioxide reductions, where such credits arelegislated. The disclosed construction material comprises at least 20%of dried filamentous algae mass, but may consist of up to 100% of driedalgae mass.

Suitable algae for use in construction material are filamentous species,which grow in strings of connected cells. Filamentous algae may bebranching, or non-branching, and may be referred to as hair algae orstring algae.

Several genera of green algae from the order Zygnematales have beenfound suitable for use in construction. More specifically, species fromthe genera of the Spirogyra, the Zygnema, and the Mougeotia, have allbeen found to have desirable characteristics for use in insulationmaterial.

Other suitable algae are species from the Cladophora, a genus ofreticulated filamentous green algae from the order of Cladophorales,specifically the Cladophora fracta. Species from the Ulothrix, from theorder of Ulotrichales, have also been found suitable for constructionuse. Hydrodictyon of the family Hydrodictyaceae from the orderChlorococcales are suitable due to their usually pentagonal or hexagonalmesh that they form. Cladophorales, Ulotrichales, Oedogonium,Chlorococcales and Zygnematales are all green algae from the class ofChlorophyceae. Klebsormidium is a green algae of the class ofKlebsormidiophyceae. Vaucheria, a genus of Xanthophyceae or yellow-greenalgae, characterized by multinucleate tubular branches lacking crosswalls have also been found suitable for use in construction material.

Further usable as a filler within construction material are species fromthe Aulacoseira from the order of Aulacoseirales, species of theMelosira from the order of Melosirales, species from the Oscillatoriafrom the order of Nostocales, as well as species within the order ofTribonematales. Aulacoseirales and Melosirales belong to the class ofCoscinodiscophyceae, Nostocales to the class of Cyanophyceae andTribonematales to the class of Xanthophyceae.

The disclosed filamentous algae are relatively easy to cultivate andharvest. When dried, the resulting algae mass forms a material that hasgood thermal insulation characteristics. Beneficial thermal insulationproperties are caused by small cavities within the algae mass. Thesecavities are small enough to not allow any significant convective heattransfer. Also, the disclosed algae comprise hollow cores, which act asnatural insulation. The insulating characteristic of these hollow coresis similar to small cavities that can be found in the hair of polarbears or chamois, causing their fur to be insulating and allowing themto survive in very cold environment.

The species or combination of species of algae that is best used forproducing insulation material depends on several environmental factors,such as for example temperature, sun intensity, and water hardness.Hence, it is desirable to analyze regional environmental factors todecide the most suitable species of algae or combination of species ofalgae that can be optimally grown at a given location.

The disclosed construction material made of dried algae mass isnaturally self-extinguishing, in spite of a relatively high carboncontent. This makes the disclosed material ideal for use inconstruction, where fire retardant characteristics are important.

While filamentous green algae species form the basis of the disclosedconstruction material, filler material may be used to fill smallcavities within dried mass of filamentous green algae. Filler materialmay for example be amorphous silica which is added as a powder to thegreen algae mass. Another suitable filler material is diatom algae mass.Diatom algae may be grown jointly with the filamentous species for usein construction material. Especially diatom algae species of theAulacoseirales and Melosirales whose cell wall comprises silicon dioxide(silica) form a desirable filler, which increases the self-extinguishingcapability of the resulting construction material. By jointly growingfilamentous and diatom algae, the diatom algae naturally adhere to thefilamentous species, so they can easily be dried and processed with thediatom species.

Algae that are harvested from a cultivation plant must be cleaned anddried before they can be formed into construction material. Drying canbe achieved simply by natural air drying, preferably leaving the wetalgae mass exposed to sunlight. Alternatively, the algae mass can beconvectively dried using hot air. The algae mass can also be vacuumdried or freeze-dried (lyophilized. Vacuum drying, in which the wetalgae mass is heated while vapor is removed through a vacuum system, isespecially beneficial, as it promotes the generation of small cavitieswithin the dried algae mass, thereby improving its thermal insulatingcapability.

Dried algae mass is processed for use in various applications, such asfor example to form upholstery material, insulating or noise-absorbingmats, fleece, packaging material, and textiles. Algae-based products aresuitable for use in construction and automotive, among others. In someapplications, dried algae mass, which forms a fibrous web, may be useddirectly, simply by cutting or otherwise forming it into a desirableshape.

For use in other applications the dried algae mass is further processed.Dried algae mass may be wrapped with a wrapping material, so that thedried algae mass is mechanically and chemically protected. Additionally,the dried algae mass may be coated with silicon dioxide, before beingwrapped.

A composite material may be formed by combining dried algae mass with anadditive, e.g. Epoxy. The consistency of dried algae material may alsobe affected by adding a binding agent such as potato starch or cornstarch. An exemplary composite material comprises pieces of isotropicgreen algae, which are attached to each other by a binding agent. Gasbubbles may be injected into the composite material to increase itsthermal insulation capability.

Several layers of dried algae mass may be used to form a multi-layerstructure, the layers being connected to each other by a binding agent.To form a mechanically strong composite material, algae having apredominant orientation may be used in several layers. The algae in eachlayer are preferably arranged such, that their predominant orientationis non-parallel, and preferably approximately perpendicular to eachother. An exemplary construction material comprises two layers of algaefrom the Zygnematales, their predominant orientation being approximatelyperpendicular to each other, and one layer of algae from theChlorococcales, for example Hydrodictyon, which have a mesh-likestructure.

Dried algae mass can be used to form insulation panels. The insulationpanels preferably have a body made of 20% or more dried algae mass. Thebody is shaped to form honeycomb-shaped chambers, which are sealed by afoil that is attached to, e.g. laminated onto, the body.

Depending on the desired characteristics of the insulation panel, thehoneycomb-shaped chambers may be evacuated, or may be filled withvarious materials. Evacuation or filling with dried algae mass producesinsulation panels having good thermal insulation. Sand, gel, or othernoise-absorbing filling materials may be used to provide good noiseinsulation (noise attenuation) characteristics.

Insulation panels may be constructed of two or more layers comprisinghoneycomb-shaped chambers. Each layer may be dedicated to a particularpurpose. For example, the chambers in a first layer may be evacuated toprovide good thermal insulation, whereas the chambers in a second layermay be filled with sand to provide good noise insulation.

Dried algae mass can further be converted into carbon fiber materialthrough pyrolysis, creating mechanically strong carbon fibers from driedalgae. Among many potential uses for pyrolytically created carbon fibermaterial made of algae mass is use as an additive in insulationmaterials to create tarnish capable of absorbing infrared radiation.Layers of pyrolyzed green algae may be combined by adding a bindingagent as described with reference to non-pyrolyzed algae mass above.

Algae mass for use in construction is produced in algae cultivationplants. Algae need water, carbon dioxide (CO₂), light, and nutrients togrow. Those are provided in an open algae cultivation pond, which isexposed to the sun. The algae cultivation pond is filled with watersuitable for growing algae, for example pre-treated waste water from asewer plant. Pre-treated waste water has at least gone through amechanical cleaning process, during which solid contaminants have beenremoved from the waste water. Carbon dioxide is injected into the algaecultivation pond through a gas inlet. The carbon dioxide may beextracted from the flue gas of a fossil fuel fired power plant, or fromexhaust gas of any other fuel burning facility. Alternatively, flue gasthat is rich in carbon dioxide from a fossil fuel fired power plant maydirectly be injected into the algae cultivation pond without priorextraction of carbon dioxide there from. A gas is considered rich incarbon dioxide, if the concentration of carbon dioxide therein is atleast 0.1% by volume. This equals about three times the concentration ofcarbon dioxide that is naturally occurring in the atmosphere, which isapproximately 0.0387% by volume. The amount of carbon dioxide that isinjected into the algae cultivation pond is electronically controlledusing a microcontroller and sensors. Electric conductivity of the wateris measured by sensors to determine the amount of nutrients in thewater. An exemplary value of the minimal amount of phosphorus (P) neededto grow algae is 10 μg P/l. For optimal growth 5-10 mg P/l are needed.The consumption of phosphorus with a full day of solar radiation isabout 250-500 mg P m²/day. Algae grow in the algae cultivation pond whenit is exposed to sunlight, typically at a rate up to 100 times fasterthan other known renewable resources.

When a sufficiently thick layer of algae slick has formed in the algaecultivation pond, the algae are automatically harvested. The thicknessof an algae slick floating in an algae cultivation pond is determined bysensors, which sense the amount of light transmitted through the algaeslick by comparing a light intensity reading above and below the algaeslick in the algae cultivation pond. If the thickness of algae slick hasreached or exceeds a predetermined threshold, the algae are harvested,preferably automatically.

Several alternative concepts for harvesting algae, referred to asgravitational harvest, net harvest, rake harvest, circulation andoverflow harvest and a harvesting machine are disclosed.

Algae cultivation plants employing gravitational harvest utilize analgae cultivation pond which has a sloped floor and a pivotable dam wallat its deep end. During an algae growth period the dam wall is closed,and the pond is filled with water that has a high concentration ofphosphates, nitrates, and other nutrients, allowing algae to grow. Toharvest algae from the algae cultivation pond its pivotable dam wall isopened, allowing the content of algae cultivation pond to flow downalong the sloped floor into a lower reservoir. A grill located above thelower reservoir separates the algae mass from water, making it possibleto reuse the water for a next growth cycle, while extracting the algaemass from the grill. Also, the algae mass may be allowed to dry on thegrill. Subsequently algae mass may be collected from the grill, andsubsequently dried, and processed into thermal insulation material orpadding material. Two of more algae cultivation ponds may form acascading set of algae cultivation ponds, wherein water and algae flowfrom an upper pond into a lower pond, when the pivotable dam wall of theupper pond is opened.

Algae cultivation plants based on net harvest comprise an algaecultivation pond, into which a net is lowered at the beginning of analgae growth cycle. Algae grow in the algae cultivation pond above thenet. Net positioning sliders position the net in a submerged position atthe bottom of the algae cultivation pond while algae are growing abovethe net. Algae are harvested by lifting the net positioning sliders intoan upper position, allowing the net to emerge. Next, the net is pulled,conveying the algae from the cultivation pond to an adjacent collectorreservoir, where the algae mass is allowed to dry on the net.

An algae cultivation plant based on circulation harvest comprises analgae cultivation pond which is surrounded by a wall. A circulationwater inlet located at one end of the algae cultivation pond, andoverflow rim located at the opposite end. The top of the overflow rim isthe lowest point of the wall surrounding the algae cultivation pond, sothat any excess water flows out of the algae cultivation pond over theoverflow rim. The overflow rim comprises a sloped wall, so that thespeed of water flowing over the rim successively increases until itflows over the rim. A conveyor system is located in a collectorreservoir adjacent to and underneath the overflow rim. During operation,water circulates from a collector reservoir underneath the conveyorsystem through the circulation water inlet into the algae cultivationpond, and across the overflow rim back into the collector reservoir.Algae slick floating with the circulating water flows across theoverflow rim, and lands on the conveyor system, where it is separatedfrom the water. The algae mass is conveyed by the conveyor system to acollection location for further processing.

The algae cultivation plant based on circulation harvest can be operatedin a continuous operating mode, wherein the water level in the algaecultivation pond is kept high, so that algae continuously flows acrossthe overflow rim onto the conveyor system. The plant can also beoperated in a burst mode, wherein the water level in the algaecultivation pond is kept below the overflow rim during an algae growthphase and wherein water is added to the algae cultivation pond during aharvest phase, causing algae growing in the algae cultivation pond toflow across the overflow rim and onto the conveyor system.

An algae cultivation plant based on rake harvest comprises an algaecultivation pond surround by a wall. An overflow rim located at one endof the algae cultivation pond, the top of the overflow rim being thelowest point of the wall surrounds the algae cultivation pond. Aconveyor is located in a collector reservoir adjacent and underneath theoverflow rim. A floating rake, which is attached to a pulley system, isused to pull algae slick growing in the algae cultivation pond acrossthe overflow rim and onto the conveyor.

In another alternative, algae growing in an algae cultivation pond canbe harvested by an algae harvesting machine, which moves across a longand narrow algae cultivation pond. As the algae harvesting machine movesacross the pond, algae slick is lifted from the surface of the algaecultivation pond and conveyed for collection outside the pond. Theharvesting machine uses a harvesting barrel having circumferentially andaxially spaced spikes to lift the algae slick from an algae cultivationpond. A conveyor barrel, located adjacent to the harvesting barrel,transports the algae slick from the harvesting barrel to a slide. At thebottom of the slide is a conveyor belt for moving the algae slick forcollection outside of the algae cultivation pond.

Algae mass produced in an algae cultivation plant can be weighed on ascale to calculate the amount of carbon dioxide that is bound in thealgae mass. The amount of carbon dioxide that has been absorbed in thealgae can be calculated by multiplying the dried mass of the algae masswith a multiplication factor, which is specific for each species ofalgae, and generally around two. The bound carbon dioxide mass may bereported to obtain tax credits, carbon emission certificates, or anyother financial benefit.

The disclosed algae cultivation plants are based on a common method forproducing green algae mass, which comprises several steps. A first stepis to provide an algae cultivation pond filled with water in which thegreen algae can grow. Algae or algae spores are provided in the algaecultivation pond to start the growth of algae. The algae cultivationpond may for example comprise spikes to which a small amount of algaeattach and remain attached even when algae are harvested from the algaecultivation pond. The algae attached to the spikes provide a basis forsuccessive harvest cycles. The algae cultivation pond is filled withwater and exposed to sunlight, allowing algae to grow therein. To fosteralgae growth carbon dioxide from an exhaust gas of a fuel burningfacility is injected into the algae cultivation pond. Alternatively,carbon dioxide may be injected into water outside the algae cultivationpond, and the carbon-dioxide saturated water inserted into the algaecultivation pond. The growth of algae in the algae cultivation pond issensed, and algae are harvested from the algae cultivation pond when asufficiently thick layer of algae has formed. Harvested algae are driedto form a green algae mass, for example by air-drying, freeze drying, orvacuum drying.

Nutrients to facilitate algae growth may be provided by injectingpre-treated waste water into the algae cultivation pond. Algae mass maybe weighed and an amount of carbon dioxide absorbed within the greenalgae mass may be calculated for the purpose of obtaining a financialbenefit associated with reducing carbon dioxide emissions into theatmosphere, e.g. to avoid having to purchase carbon emissioncertificates.

The following detailed description of the invention is merely exemplaryin nature and is not intended to limit the invention or the applicationand uses of the invention. Furthermore, there is no intention to bebound by any theory presented in the preceding background of theinvention or the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an algae cultivation plant.

FIG. 2 is a schematic illustration of an algae cultivation plant showingadditional details.

FIG. 3 illustrates a measurement and control device for algaecultivation in an open growth facility.

FIG. 4 shows an algae cultivation plant suitable for use in even terrainutilizing meshwork harvesting.

FIG. 5 a illustrates the structure of a Spirogyra alga.

FIG. 5 b shows a cross section through a Spirogyra alga.

FIG. 6 a shows an algae mat.

FIG. 6 b is a cross section through two algae mats.

FIG. 6 c is a top view of the two algae mats of FIG. 6 b.

FIG. 6 d illustrates a processed algae mat.

FIG. 7 a shows a schematic top view of a water net algae.

FIG. 7 b is a cross section of a laminate algae mat.

FIG. 7 c is a top view of the composite material of FIG. 7 b.

FIG. 8 a shows a cross section and a top view of the isotropic algaemass.

FIG. 8 b shows sections of algae mass.

FIG. 8 c shows an insulation material.

FIG. 9 a is a top view of a honeycombed structure for an insulation mat.

FIG. 9 b is a cross section of the mat of FIG. 9 a.

FIG. 9 c shows a magnified cross section through the mat of FIG. 9 a.

FIG. 10 a is a top view showing a honeycombed structure for a insulationmat.

FIG. 10 b is a cross section through the mat of FIG. 10 a.

FIG. 10 c is a cross section trough an arrangement having two insulationmats.

FIG. 11 a shows an embodiment of an insulation material.

FIG. 11 b shows an alternative embodiment of an insulation material.

FIG. 12 shows an algae cultivation pond which is suitable for use inflat terrain.

FIG. 13 illustrates harvesting of algae in an algae cultivation pond.

FIG. 14 a is a side view of a harvesting machine for algae in an algaecultivation pond.

FIG. 14 b is a front view of the harvesting machine of FIG. 14 a.

FIG. 15 is a block diagram showing a method for producing carbon fiberfrom algae mass.

DETAILED DESCRIPTION

An exemplary use of filamentous algae for construction is explained withreference to Spirogyra algae, one of many filamentous algae that aresuitable for use in construction, as illustrated in FIG. 5 a. Spirogyraalgae 500 are unbranched with cylindrical cells connected end to end inlong green filaments. Cell wall 501 comprises an outer wall of celluloseand an inner wall of pectin. A ribbon shaped, serrated or scalloped, andspirally arranged chloroplast 502 is embedded within cell wall 501. Cellwall 501 further comprises nitrogen, causing spirogyra algae 500 to beself-extinguishing.

As illustrated in cross sectional view FIG. 5 b a cavity 503 is formedby cell wall 501 and chloroplast 502. The average diameter 504 ofSpirogyra algae 500 is approximately 30 micrometer. When dried, cavity503 is filled with air. The small diameter 504 of the dried Spirogyraalgae 500 reduces the possible convective flow of air within cavity 503,causing Spirogyra algae 500 to act as a natural heat insulator.

Diameter 504 of a Spirogyra alga is approximately 5 times larger thanthe diameter of artificially created carbon fibers, which have adiameter of approximately 6 micrometers. However, other than artificialfiber, the mass of the Spirogyra alga is concentrated along its outerdiameter at cell wall 501, a structure that is almost impossible toartificially create. When dried, Spirogyra algae 500 have a very lowdensity of approximately 0.06 g/cm³. Dried spirogyra algae mass has alarge ratio of surface area to weight, which results in high robustnessfor products, e.g. composite materials, made of spirogyra algae mass.The physical structure of filamentous algae is similar to that of bambooplants, in that the plant's mass is concentrated along its outerdiameter, resulting in a lightweight, but mechanically robust structure.A similar structure can be found e.g. in Spirogyra, Zygnema, Mougeotia,or Cladophora algae.

As illustrated in FIG. 6 a, algae from the order Zygnematales, whendried, assume a form of a naturally fibrous algae mat 601. In calm orevenly moving water Zygnematales naturally grow in form of threads whichare oriented parallel to each other. This allows algae mat 601 to beused as fleece, felt or insulation material simply by cutting orotherwise shaping it into a desired shape. Other renewable fibers, e.g.those from wood, have to be mechanically processed in energy consumingcutting processes, to achieve the same structure. The algae within algaemat 601 have a predominant orientation 602 of their cells due toanisotropic growth.

A mechanically stronger structure can be created by applying a bindingagent 606 to a first algae mat 601 and a second algae mat 603 as shownin FIG. 6 b. Binding agent 606 may for example be potato starch or cornstarch, or any other single- or multi-component binding agent known inthe art. Algae mats 601 and 603 may e.g. be soaked in a bath of bindingagent. Referring to FIG. 6 c algae mat 601 and algae mat 603 are thenplaced onto each other, such that the predominant orientation 602 ofcells in algae mat 601 is about perpendicular to the predominantorientation 604 of cells in algae mat 603. As shown in FIG. 6 d atwo-layer algae mat 605 having a first layer of cells orientedperpendicular to a second layer of cells results. The process can berepeated to create algae mats having more than two layers.

Referring now to FIG. 7, composite material 704 utilizing differentspecies of algae is disclosed. An exemplary composite material shown inFIG. 7 b comprises three layers of algae. A center layer 701 comprisesHydrodictyon reticulatum in the family Hydrodictyaceae from the orderChlorococcales within the class of Chlorophyceae. Hydrodictyonreticulatum form a large, usually pentagonal or hexagonal, mesh which isillustrated in FIG. 7 a. Outer layers 702 and 703 are dried algae fromthe Zygnematales, e.g. species from the genera of Spirogyra, Zygnema,Mougeotia, or Cladophora which have a fibrous, string-like, structure.

The composite material 704 as shown in FIG. 7 c combines string-shapedalgae cells in algae mats 702 and 703, and a central mesh-structure ofcells in an algae mat forming central layer 701. Algae cells in matsforming outer layers 702 and 703 are oriented about perpendicular toeach other. The resulting composite material 704 provides goodmechanical strength and resistance against tearing. Composite material704 comprising layers of algae mats in center layer 701 and outer layers702 and 703 may be manufactured by adding a binding agent (not shown) tothe algae mats in center layer 701, and outer layers 702 and 703. Thealgae mats in each layer are then placed onto each other, and pressureis applied.

Referring now to FIG. 8 a, a mass 801 of isotropic dried algae is shownin a top view and a cross sectional view. As illustrated in FIG. 8 b,algae mass 801 may be cut into several pieces 802. As shown in FIG. 8 c,a binding agent 803 is applied to the algae pieces 802, forming acomposite material 804. Composite material 804 may be processed inseveral ways to be used as an insulation material. Composite material804 may e.g. be molded or pressed.

Binding agent 803 may comprise gas bubbles, e.g. carbon dioxide that hasbeen added under pressure. During the molding or shaping of compositematerial 804 the gas bubbles within binding agent 803 may be allowed toexpand, e.g. by reducing air pressure around the composite material 804.Alternatively, a foaming agent may be added, which generates bubbleswithin composite material 804. The additional bubbles in compositematerial 804 reduce the density of composite material 804, and increaseits heat insulation performance.

Referring now to FIG. 9 a, an insulation panel 911 having a honeycombstructure is shown. The walls of insulation panel 911 may be made ofcomposite algae material or plastic. The honeycomb structure ofinsulation panel 911 comprises a plurality of honeycomb shaped chambers912, which are sealed by foil 913. Depending on the intended use ofinsulation panel 911, chambers 912 may be filled with differentmaterials. Chambers 912 may e.g. be filled with air or another gas foruse as a heat insulation mat. Even better heat insulation may beachieved by evacuating chambers 912, which requires the algae compositematerial forming insulation panel 911 to be airtight.

Chambers 912 may also be filled with a filler material 914, for exampleloose sand or plaster for use as noise attenuator. A more detailed viewof sand as filler material 914 of a chamber 912 is shown in FIG. 9 b.Sand corns 915 are loosely situated within chamber 912, allowingmovement of the sand corns through hollow areas 916. Noise energy islargely absorbed through mechanical friction of sand corns rubbingagainst each other, thereby providing good noise attenuation of theinsulation panel 911. Alternatively, chambers 912 may be filled with aliquid foam, or gel containing gas bubbles, suitable to absorb energywhen compressed by sound waves.

Referring to FIG. 10, an alternative structure utilizing several layersof honeycomb shaped algae mass are shown. An upper layer of honeycombshaped algae mat 1021 comprises upper chambers 1022 and a lower layercomprises lower chambers 1024. Upper layer and lower layer only meet atsmall intersecting areas 1030, thereby greatly limiting the possibleheat transfer between the both layers. The upper layer of algae mat 1021is covered by top foil 1023. The lower layer of algae mat 1021 iscovered by bottom foil 1025. Instead of using top foil 1023 and bottomfoil 1025 algae mat 1021 may be covered by any other form of enclosingmaterial, e.g. plasterboard or boards made of wood. Depending on theintended use upper chambers 1022 and lower chambers 1024 may be filledwith the same or different material. For example, upper chambers 1022may be filled with a noise attenuating material, while the lowerchambers 1024 are filled with a heat insulating material. The noiseattenuating material may e.g. be sand, gel, or any other noiseattenuating material known in the art. The heat insulating material maye.g. be air, expanded algae particles, or any other heat insulatingmaterial known in the art.

An alternative structure is shown in FIG. 10 c, wherein two honeycombalgae mats 1026 and 1027 such as those disclosed with reference to FIG.9 are placed onto each other. Honeycomb algae mats 1026 and 1027 areplaced in opposite orientation, such that their respective foil covers1028 are facing outside. The honeycomb chambers of mat 1026 and 1027 arepreferably displaced relative to each other by ½ of their size. Matshaving different characteristics, such as a noise attenuating mat 1026may be combined with a heat insulating mat 1027 to achieve a combinedfunctionality of a mat that is both heat insulating and noise absorbing.While an example with two mats has been shown it should be understoodthat advantageous combinations utilizing more than two mats arepossible.

While mats comprising dried algae mass have been found to besurprisingly beneficial, further improvements are possibly by pyrolizingalgae mass to form carbon fibers. Dried spirogyra algae have a carboncontent of approximately 45%. Their cell wall 501 comprises cellulose,making the algae a suitable raw material for the production of carbonfiber and carbon mats.

A method for producing carbon fiber from algae mass is illustrated inFIG. 15. In a first step 1501 algae is harvested. Next, the algae isdried in step 1502 to create dried algae mass. In the next step 1503 thedried algae mass is placed into a sealed container, wherein the algaemass is held by mounting fixtures at both ends of the sealed container.The algae mass is held under tension by the mounting fixtures. If thealgae mass has a predominant orientation of its cells, it is placed intothe container such that its cells are predominantly oriented parallel tothe tension that is created by the mounting fixture. The predominantorientation of the tubular cells of the algae later leads to apredominant orientation of carbon fibers of carbonized algae. Next, instep 1504, the container is heated and evacuated to minimize the amountof oxygen in the container, allowing the algae mass to pyrolize. Heatingof the container may occur in several steps, e.g. 600° C., 700° C., 800°C. and 900° C. Optionally, as shown in step 1505, gas created by thepyrolysis can be extracted and used as a heat source. Lastly, in step1506, the now carbonized algae material is removed from the container.

Two carbonized algae mats can further be processed by adding a bindingagent, e.g. soaking the carbonized algae mat in a binding agent, andplacing them onto each other. The two mats are preferably oriented such,that the predominant orientation of carbon fibers of carbonized algae ineach mat is perpendicular to each other.

Yet another example of algae-based insulation material is illustrated inFIG. 11 a. As illustrated, two mats 1101 and 1104 are placed onto eachother. Mats 1101 and 1104 may be algae mats having honeycomb structuredchambers as disclosed with reference to FIG. 9. Mats 1101 and 1104 mayalso be any other suitable thermoformed or pressed material. Chambers1103 within mat 1101 are filled with a filling material. The fillingmaterial comprises dried algae mass. Preferably, the filling materialcomprises dried algae mass which is mixed with silicic acid using aratio of approximately 70% dried algae mass and 30% silicic acid.Silicic acid nanoparticles are commercially available, for example fromWacker Chemie, Munich, Germany. The filling material is held in chambers1103 by foil 1102, which is placed onto mat 1101 in an evacuatedchamber, so that air is evacuated from chambers 1103 before foil 1102seals the chambers. The low pressure surrounding the filling material inchambers 1103 causes foil 1102 to bend concavely into chambers 1103 whenmat 1101 is exposed to standard ambient air pressure.

Place onto mat 1101 is a slightly smaller mat 1104, having one fewerchamber along its diameter than mat 1101. Mat 1104 is placed onto mat1101 with an offset, such that the center of a chamber 1103 is about onehalf of a chamber width offset from the center of a chamber 1106 of mat1104. Chambers 1106 can be filled with dried algae mass, which providesgood heat insulation. Chambers 1106 may also be filled with sand orgypsum, thereby providing noise attenuation. Alternatively, chambers1106 may be filled with a mixture of dried algae mass and sand orgypsum. Filling material is added to a level which is below the sidewalls height, such that sealing foil 1105 can form a concave indentationabove each chamber 1106. The slightly concave shape of sealing foil 1105above each chamber 1106 guarantees, that sealing foil 1105 touches uppermat 1101 only at the vertical walls around each chamber 1106 of lowermat 1104. The limited contact of sealing foil 1105 with upper mat 1101reduces thermal conductivity through the insulation panel 1100.

Upper mat 1101 and lower mat 1104 are enclosed by an air sealedcontainer which forms the out wall of insulation panel 1100. A lowercontainer tub 1107 is sealed by a container lid 1108. Insulation panel1100 may be evacuated, removing air between the walls of container 1107,1108 and the upper mat 1101 and lower mat 1104. Container tub 1107 andlid 1108 can be made of metalized synthetic foils. Two or more identicalinsulation panels 1100 may be placed adjacent to each other, every otherpanel being placed upside down, so that the wider upper mat 1101 of afirst panel extends over top of the smaller lower mat 1104 of anadjacent panel, forming a half lap joint between both panels.

To form larger units, insulation panels 1100 can be mounted onto asupporting board 1112, for example a drywall or plasterboard.

In another example, as illustrated in FIG. 11 b, an insulation panel1150 is provided. Insulation panel 1150 comprises two panel members, anupper panel member 1121 and a lower panel member 1122. Each panel member1121 and 1122 is preferably made of dried algae mass and a binderadditive, e.g. gypsum. Panel members 1121 and 1122 comprise wedge shapedchambers 1151, 1152. The surface area of wedge shaped chambers 1151,1152 may optionally be treated, e.g. by applying a metallization layermade of aluminum.

Depending on the intended application of insulation panel 1150, chambers1151 and 1152 are filled with different filling materials. As shown, thechambers 1151 of upper panel 1121 are filled with dried algae mass beingfilling material 1125. The chambers 1152 of lower panel 1122 are filledwith a mixture of dried algae mass and an additive, for example sand,gypsum powder, nanomaterial, silicic acid, or dried diatom algae, etc.

Chambers 1151 of upper panel member 1121 are sealed with foil 1123.Preferably, air is evacuated from the upper chamber 1151 before foil1123 is applied, so that the air pressure in chambers 1151 is about 30mbar. Correspondingly chambers 1152 of lower panel member 1122 aresealed by foil 1124. The low air pressure within chambers 1151 and 1152reduced convective heat transport through panel 1150, thereby improvingits heat insulation capability. When exposed to ambient air pressure oftypically 1013 mbar foils 1123 and 1124 are pushed into chambers 1151,1152, forming a characteristic concave shape above each chamber. Upperpanel member 1121 and lower panel member 1122 are placed onto eachother, so that chambers 1151 and chambers 1152 face each other and aredisplaced against each other with an offset of approximately ½ chamberwidth.

Upper panel member 1121 and lower panel member 1122 may be assembled ina low atmospheric pressure environment of e.g. 100 mbar. In this examplean external seal 1131 around the panel between upper foil 1123 and lowerfoil 1124 is created. This causes only a small relative pressuredifference between air in the chambers 1151, 1152 of about 30 mbar andair between upper panel member 1121 and lower panel member 1122 of about100 mbar. Consequently, the concave indentation of upper foil 1123 andlower foil 1124 is less pronounced, as is illustrated in broken line1127 and 1128. This gives the filling material 1125 and 1126 withinchambers 1151 and 1152 some room to move within the chambers. Theability of filling material 1126 to move within chamber 1152 isdesirable to provide noise attenuation. Noise energy can be absorbed bysmall relative movement of the dried algae mixture with sand or gypsumbeing filling material 1126. The material can be tuned to optimize noiseabsorption in a particular audio frequency by variation of pressurewithin chambers 1152 and the pressure between upper panel member 1121and lower panel member 1122. Upper panel member 1121 and lower panelmember 1122 only contact each other at surround seal 1131 of upper foil1123 and lower foil 1124. The reduced contact surface between upperpanel member 1121 and lower panel member 1122 provides good thermal andnoise insulation.

Luckily, green algae that are suitable for use in insulation materialare relatively easy to grow. Several alternative algae cultivationplants, as well as harvesting methods and machines are disclosed, whichcan produce green algae for use in insulation material as describedabove. As part of the carbon cycle green algae absorb carbon dioxide andwater under sunlight to produce carbohydrate energy, leaving oxygen as abyproduct. Hence it is desirable to combine algae cultivation plantswith fossil fuel burning facilities, for example power plants or otherindustrial facilities that generate carbon dioxide. The algaecultivation plant in such a combination absorbs some of all of thecarbon dioxide that is generated by the power plant or industrialfacility, thereby reducing the carbon dioxide emissions. The ability toreduce carbon dioxide emissions is of particular interest injurisdictions that regulate carbon dioxide emissions, possibly taxingsuch emissions, for example by requiring an emitter to purchase carbondioxide emission rights.

Referring to FIG. 1, a diagram of an exemplary algae cultivation plantin combination with a carbon dioxide generating facility is illustratedgenerally. The exemplary plant includes a cascading set of algaecultivation ponds 107 having sloped floors 115. The ponds are filledwith water that is rich in phosphates, nitrates, and other nutrients.More specifically, the ponds may be filled with pre-treated waste water104 from a sewer plant or another source. Water in algae cultivationponds 107 circulates trough circulation pump 113. The water in ponds 107is rich in nutrients for cultivating algae and contains algae spores.

Carbon dioxide from a fuel burning power plant is extracted from thepower plant's flue gas. The fuel burning power plant may for example bea fossil fuel burning power plant such as a gar or coal power plant. Thefuel burning power plant may also be a biogas burning power plant. Acarbon dioxide extractor and distributor 103 extracts carbon dioxidefrom the power plant's flue 102 and pumps carbon dioxide into carbondioxide storage tank 101, gas inlet pipes 110, or both. Carbon dioxidestorage tank 101 is used to store carbon dioxide for use duringdowntimes when the power plant is not operating. Carbon dioxide fromeither the flue 102 or carbon dioxide storage tank 101 is pumped throughextractor and distributor 103 and injected into algae cultivation ponds107 through gas inlet pipes 110. Alternatively, the step of extractingcarbon dioxide from the flue gas may be omitted, and flue gas that isrich in carbon dioxide may directly be pumped from flue 102 into carbondioxide storage tank 101 or gas inlet pipes 110 for injection into algaecultivation ponds 107. A gas is considered rich in carbon dioxide, ifthe concentration of carbon dioxide therein is at least 0.1% by volume.This equals about three times the concentration of carbon dioxide thatis naturally occurring in the atmosphere, which is approximately 0.0387%by volume.

The amount of carbon dioxide or flue gas that is injected into algaecultivation ponds 107 is controlled by a control system based on severalinputs. Among the inputs of the control system are one or more of thewater level in ponds 107, temperature of the water in ponds 107, acidityof the water in ponds 107, intensity of sunlight 116, and sunlightintensity in pond 107 below algae slick 109, to create optimal growthconditions for algae in ponds 107.

The control system may further comprise sensors for sensing air pressureand water pressure in the algae cultivation ponds 107 and control thepressure of carbon dioxide or flue gas in gas inlet pipes 110 to bebelow the sum of air and water pressure, thereby avoiding excess carbondioxide or flue gas to escape through algae cultivation ponds 107.

The control system comprises tables stored in electronic memory,correlating sensors inputs for sunlight intensity, water oxygensaturation and water acidity in ponds 107 with an optimal carbon dioxideor flue gas injection rate. For example, the amount of carbon dioxideinjected into pond 107 increases with increasing sunlight intensity anddecreases with decreasing sunlight intensity. The data in the tables maybe empirically derived trough tests and be specific for different kindsof algae. The control system controls the amount of carbon dioxide orflue gas injected into the algae cultivation ponds 107, and the amountof waste water 104 inserted through waste water valve 105 and wastewater inlet 106. The control system further controls the amount of water117 that is recycled through from collector basin 118 throughcirculation inlet 114 into algae cultivation pond 107.

Continuous growth of algae in algae cultivation ponds 107 leads toformation of an algae slick 109, which floats on top of the water inalgae cultivation pond 107 and prevents sunlight from penetrating thewater, thereby reducing further growth of algae in algae cultivationpond 107. Sensors (not illustrated) determine the thickness of algaeslick 109 and generate a signal, once a predetermined thickness has beenreached. Responsive to the signal, the injection of carbon dioxide orflue gas into algae cultivation pond 107 is stopped, and gravitationalharvest of the algae is initiated. Thickness of the algae slick 109 maybe determined by comparing sunlight intensity measured by a first sensoroutside the algae cultivation pond 107 with sunlight intensity measuredby a second sensor within the algae cultivation pond 107. The secondsensor is located within the algae cultivation pond 107 below the algaeslick 109. A large difference in sunlight intensity between the firstand the second sensor indicates a thick, light absorbing algae slick109. Instead of utilizing sunlight, an artificial light source (notshown) may be used to determine the thickness of algae slick 109.

A carbon dioxide sensor may be located above the water level of algaecultivation pond 107 to reduce or stop the injection of carbon dioxideor flue gas into algae cultivation pond 107, if increased levels ofcarbon dioxide are measured to be escaping algae cultivation pond 107.

Algae cultivation ponds 107 comprise a sloped floor 115 and a pivotabledam wall 108. Algae are harvested by opening pivotable dam walls 108,which pivot in a downhill direction, allowing water and algae slick 109to flow downhill from algae cultivation ponds 107 into a collector basin118. Grill 112 is used to separate algae mass 111 from the water. Aswater and algae slick 109 from ponds 107 slides downhill the slopedfloor 115 of ponds 107 into collector basin 118 algae mass 111 is caughton grill 112, while water 117 flows through grill 112 into collectorbasin 118. Algae mass 111 may be left on grill 112 to dry, and beremoved from grill 112 for further processing.

Water 117 may be recycled by pumping water 117 from collector basin 118through circulation pump 113 and circulation inlet 114 back into pond107.

If flue gas from flue 102 is directly injected into ponds 107, itbeneficially heats the water in ponds 107, thereby causing optimalconditions for algae growth.

An aerator device 119 may be operatively connected to the outlet ofcarbon dioxide carrying gas inlet pipe 110 into ponds 107. Aeratordevice 119, which may be a membrane comprising small holes, causescarbon dioxide or flue gas from gas inlet pipe 110 to form small bubbleswhen injected into pond 107. These bubbles support a uniform saturationof pond 107 with carbon dioxide. They further spread sunlight enteringpond 107, causing an increases photosynthesis activity of the algaegrowing in pond 107.

Opening and closing pivotable dam walls 108 causes alternating growthand harvesting cycles, wherein the pivotable dam walls 108 are closedand ponds 107 are filled with water during a growth cycle and pivotabledam walls 108 are opened during a harvesting cycle.

Algae mass 111 that has been removed from grill 112 may be dried andprocesses into construction material as described above. Algae mass 111may also be utilized as a resource for pharmaceutical, medical orcosmetic use. Algae mass 111 may further be used as a resource foranimal food, renewable fuel, fertilizer, or natural fiber constructionmaterial.

An alternative algae cultivation plant using an indirect injection ofcarbon dioxide is disclosed with reference to FIG. 2. Several algaecultivation ponds 207 are provided, arranged in a cascade along theslope of a hill or mountain, each having a wall 208 that can be lowered.Below the last cultivation pond 207 is an overflow and mixing reservoir,which is adapted to inject carbon dioxide and nutrients for algaecultivation thereto. Water circulates from circulation inlet 214 intothe uppermost cultivation pond 207, through the cascading set ofcultivation ponds 207, and the overflow and mixing reservoir 224. Thecirculation is facilitated by circulation pump 213, which pumps waterfrom the overflow and mixing reservoir 224 uphill to circulation inlet214 and the uppermost cultivation pond 207.

To grow, algae need water, nutrients, carbon dioxide, and sunlight. Theopen structure of algae cultivation ponds 207 exposes algae to sunlight216. Alternatively algae cultivation pond 207 may be underneath atransparent cover through which sunlight can enter the algae cultivationpond 207. The sunlight exposure may be amplified by placing reflectivematerial onto the floor of algae cultivation ponds 207, thereby exposingalgae not only to the direct sunlight 216, but also to light that isreflected of the floor of algae cultivation ponds 207. Alternatively,algae cultivation ponds 207 may be made of a reflective material, e.g.stainless steel or alloy to achieve the same effect.

Nutrients are added to the water in cultivation ponds 207 throughoverflow and mixing reservoir 224. Nutrients may specifically includephosphates and nitrates, which can be a side product of sewer plants.Water that is rich in nutrients is pumped through pipe 204 and pump 205and inlet 206 into a heating reservoir 221. Pump 218 has an inlet pipe219 which reaches into heating reservoir 221. Pump 218 pumps warm,nutrient rich water from heating reservoir 221 through outlet pipe 217into overflow and mixing reservoir 224, where it enters the watercirculation through cultivation ponds 207.

The necessary carbon dioxide to stimulate growth of algae in algaecultivation ponds 207 stems from a powerplant or other facilityproducing gas that is rich in carbon dioxide. Carbon dioxide rich gas isdiverted from flue 202 to compressor 203, where the gas is compressed toabout 6.5 bar. Through gas pipe 222 the warm, carbon dioxide rich gas ispumped through a heat exchanger in heating reservoir 221, therebycooling the gas in gas pipe 222 and heating the nutrient rich water inheating reservoir 221. Through a control valve 225, which also acts as acheck valve, the carbon dioxide rich gas is injected into an undergroundwater reservoir 201. Underground water reservoir 201 is a sealedpressure container. Overflow and mixing reservoir 224 and undergroundwater reservoir 201 are connected by pipe 210. Underground waterreservoir 201 is located lower than the open overflow and mixingreservoir 224, for example 60 meters below the overflow and mixingreservoir 224. Consequently, the pressure in underground water reservoir201 is approximately ΔP=6 bar above the pressure at the bottom ofoverflow and mixing reservoir 224.

Water within the underground water reservoir 201 having a temperature of10° C. and a pressure of 6 bar can absorb 6 gram of carbon dioxide perliter. Underground water reservoir 201 can therefore store carbondioxide, for example carbon dioxide that is generated at night, when dueto lack of sunlight the algae in cultivation ponds 207 can't grow, andhence don't need any carbon dioxide. An underground reservoir holding avolume of 1000 m³ of water at 10° C. and 6 bar can store 6000 kg of CO2.Rest gas having low CO2 content can escape the underground waterreservoir 201 through pressure relieve valve 223 in pipe 220. Flowing inopposite direction, pipe 220 may also be used to add water intounderground water reservoir 201.

Assuming a temperature of 22° C. and standard atmospheric pressure of 1bar, water in overflow and mixing reservoir 224 can store only 1.5 gramof carbon dioxide per liter. Therefore, carbon dioxide rich water fromunderground water reservoir 201 is added to overflow and mixingreservoir 224 through control valve 227 at a maximum ration of 1 literof water from underground water reservoir 201 per every 3 liter of waterin overflow and mixing reservoir 224. Carbon dioxide mixed into thewater of overflow and mixing reservoir 224 enters the circulationthrough the cultivation ponds 207, where the carbon dioxide is absorbedby the growing algae.

Algae from the order Zygnematales, especially species from the genera ofthe Spirogyra, the Zygnema, and the Mougeotia, and Hydrodictyon algaefrom the order Chlorococcales grow close to the surface of cultivationponds 207, forming algae slick 209. Sunlight 216 is used for thephotosynthesis of algae slick 209, absorbing primarily blue and red,including near infrared, light. Zygnema and Spirogyra algae grow in apreferred orientation of their cells.

To harvest algae from cultivation ponds 207, the lower walls 208 ofalgae cultivation ponds 207 be lowered, so that water and algaecontained in the cultivation ponds flows downhill towards overflow andmixing reservoir 224. A grill 212 is provided above overflow and mixingreservoir 224 to capture algae mass 211 and separate it from water ofthe cultivation ponds 207. Algae mass 211 may be left on grill 212 toair dry, or removed when still wet for further processing.

The right time to harvest algae can be determined by a control system asillustrated in FIG. 3. Algae 309 grow in an algae cultivation pond 307,which is filled with water that is rich in nutrients and carbon dioxide.Algae 309 hereby forms an algae slick which floats on the water of algaecultivation pond 307. A side wall 338 having a pivotable wall segment337 is provided. An overflow gate 339 extends above pivotable wallsegment 337, allowing excess water to flow through it, while holdingalgae 309 back inside algae cultivation pond 307.

Through valve 305 and first inlet 306 an aqueous nutrient solution canbe added to algae cultivation pond 307. The aqueous nutrient solutionmay for example we water that is rich in phosphates and nitrates, atypical byproduct of sewer plants.

Through valve 313 and second inlet 314 fresh water and algae spores canbe added to algae cultivation pond 307. Second inlet 314 may also beconnected to a circulation pump to circulate water in algae cultivationpond 307.

An aerator 336 is provided, through which a gas, e.g. carbon dioxide,flue gas, air, or a mixture thereof, can be injected into algaecultivation pond 307. The amount of gas is controlled through gas inletvalve 303. The volume or mass flow of gas through gas inlet pipe 310into aerator 336 is measured by a volume flow or mass flow sensor 330.

Algae 309 grow in the presence of sunlight 316. The intensity ofsunlight 316 is measured by exterior sunlight sensor 317, which ismounted outside of algae cultivation pond 307. A second, submersed lightsensor 318 is disposed inside algae cultivation pond 307, located underalgae 309 that are floating in algae cultivation pond 307. Both exteriorsunlight sensor 317 and submersed light sensor 318 are operativelyconnected to a central control unit 319. Central control unit 319 isadapted to read data from exterior sunlight sensor 317 and submersedlight sensor 318. By comparing data from exterior sunlight sensor 317and submersed light sensor 318 underneath algae 309, the thickness ofalgae 309 can be determined. A thicker layer of algae 309 absorbs morelight, thereby leading to a larger difference in light sensed betweenexterior sunlight sensor 317 and submersed light sensor 318. Thedifference in sensor measurements between exterior sunlight sensor 317and submersed light sensor 318 is used as an input to an algorithm incentral control unit 319 which determined the right time to harvestalgae 309. A more accurate measurement may be achieved by using anartificial light source (not shown) to illuminate submersed light sensor318 trough algae 309 with a predetermined light intensity.

While exterior sunlight sensor 317 and submersed light sensor 318 areused to determine sufficient thickness of algae 309 for harvest,information from one or both of these sensors is also used to determinethe correct amount of carbon dioxide to inject through aerator 336 intoalgae cultivation pond 307. The amount of carbon dioxide that can beprocessed by photosynthesis in algae 309 depends on the amount ofsunlight 316, and changes over the course of a day. At night, exteriorsunlight sensor 317 detects the absence of sunlight 316. Central controlunit 319, responsive to a signal from exterior sunlight sensor 317indicating darkness, closes gas inlet valve 303 through its output 327.

Central control unit 319 is an industrial control system, such as aprogrammable logic controller. Central control unit 319 comprises amicrocontroller, power supply, electronic memory, and input and outputcircuitry such as for example A/D converters, D/A converters, and PWMsignal generators. Central control unit 319 is powered through powerinput 324.

Central control unit 319 also determines and control optimal growthconditions for algae 309. Operatively connected to central control unit319 is further a temperature sensor 320, configured to measure thetemperature of water inside algae cultivation pond 307. A pH probe 321is also operatively connected to central control unit 319 and adapted tomeasure the acidity of water in algae cultivation pond 307.

An external CO₂ sensor 322 is provided outside algae cultivation pond307, positioned such that it can sense carbon dioxide concentrationaround algae cultivation pond 307, the CO₂ sensor 322 being operativelyconnected to central control unit 319. If elevated carbon dioxide levelsare sensed by CO₂ sensor 322, central control unit 319 reduces theinflow of carbon dioxide into algae cultivation pond 307 through aerator336 by closing gas inlet valve 303. Potentially dangerous levels of CO₂sensed by CO₂ sensor 322 can trigger an visual or audible alarm,alerting personnel of a potential health risk around algae cultivationpond 307.

Outputs 325 through 329 of central control unit 319 are connected to thevarious actuators of the system. More specifically, output 325 isoperatively connected to valve 305, providing central control unit 319control over the inflow of nutrients into algae cultivation pond 307.Output 326 is operatively connected to valve 313, providing centralcontrol unit 319 control over the inflow of fresh water, or watercirculation into algae cultivation pond 307. Output 327 is operativelyconnected to gas inlet valve 303, providing central control unit 319control over the flow of carbon dioxide into algae cultivation pond 307.Output 328 is operatively connected to pivotable wall segment 337,allowing central control unit 319 to open algae cultivation pond 307 sothat algae and water flow out. Lastly, output 329 provides a diagnosticinterface for use with a diagnostic control device (not shown).

An external input 323 is used to program central control unit 319. Theexternal input may e.g. be a connection to a computer system fordownloading tables of empirically gathered data that correlate sensordata from one or more of sensors which are operatively connected tocentral control unit 319 with a suitable carbon dioxide volume flow.Central control unit 319 in this example controls gas inlet valve 303,using feedback from mass flow sensor 330, to achieve a predeterminedflow of carbon dioxide through aerator 336 into algae cultivation pond307. The target value of carbon dioxide flow is determined through oneor more lookup tables, which correlate sensor inputs with a targetvolume flow of carbon dioxide.

Alternatively, external input 323 may provide a pH setpoint. In thisexample central control unit 319 controls the acidity water inside algaecultivation pond 307. For some green algae, the water acidity, measuredby pH probe 321, is kept preferably between pH 6.0 and 9.2. A maxacidity of pH 10.0 should not be exceeded to prevent damage to the algaein algae cultivation pond 307. The acidity of water in algae cultivationpond 307 is controlled by increasing or decreasing the amount of carbondioxide that enters algae cultivation pond 307 through gas inlet valve303. If the water in algae cultivation pond becomes too acidic, centralcontrol unit 319 adds fresh water by controlling valve 313.

Central control unit 319 may be connected to additional sensors, e.g. anatmospheric pressure sensor, or a water pressure sensor (not shown).Central control unit 319 may comprise programmable operating parameters,e.g. water hardness of water in algae cultivation pond 307, which can bedetermined through manual tests and entered manually into centralcontrol unit 319.

Central control unit 319 is configured to create optimal growthconditions for a particular species of algae to be grown in algaecultivation pond 307. Algae species from the genera of the Spirogyra,for example, thrive in water having a temperature of 25° Celsius, and apH-value of between 6.2 and 8.2, preferably 7.2. The ideal acidity ofwater to foster growth of Spirogyra algae depends on its hardness, asillustrated in the table below:

Carbonate hardness pH value  7 6.8 11 7.0 14 7.1Central control unit 319 is configured to regulate acidity of the waterto a predetermined target level, which is configured for eachinstallation of an algae cultivation pond based on the hardness of waterto be used in the algae cultivation pond.

Referring now to FIG. 4, an alternative design for cultivating andprocessing algae using net harvest is illustrated. The algae cultivationponds shown in FIG. 1, FIG. 2 and FIG. 3 utilize gravitational harvest,in which algae is harvested by opening an algae cultivation pond,allowing its content to flow down a slope through a harvesting grill. Incontrast, the design illustrated in FIG. 4 does not need a slopedarrangement of algae cultivation ponds, and leans itself for use in flatterrain.

An algae cultivation pond 401 is provided, which is located adjacent toa collector reservoir 402 of similar size. A net 403 is provided, thewidth of which extends across algae cultivation pond 401. Net 403 isrolled into a roll 409, which is located at one end of algae cultivationpond 401. Net 403 extends along algae cultivation pond 401 and collectorreservoir 402. Net 403 is connected to a pulling device 407 located atthe opposite end of collector reservoir 402. Net positioning sliders 404are provided, through which net 403 can be pushed to the bottom of algaecultivation pond 401 or collector reservoir 402. FIG. 4 shows net 403being positioned at the bottom of algae cultivation pond 401 by netpositioning sliders 404, which are in their lowered position.

Algae cultivation pond 401 uses the water circulation, carbon dioxideinjection, and control concepts described with reference to FIG. 1, FIG.2 and FIG. 3 above. For simplicity, those are not shown in FIG. 4.

To cultivate algae, net 403 is lowered towards the bottom of algaecultivation pond 401 by lowering net positioning sliders 404. This isdone before any algae are allowed to grow in algae cultivation pond 401.Algae are then allowed to grow in algae cultivation pond 401 byinjecting algae spores, carbon dioxide, and nutrients are described.Once algae 405 have grown sufficiently thick, they are harvested.

To harvest algae 405, net positioning sliders 404 are lifted into theirupper position, which is above the water level of water in algaecultivation pond 401. Pulling device 407 is activated, thereby liftingnet 403 out of algae cultivation pond 401, conveying algae 405 intoposition of algae mass 406. Algae mass 406 is left in position abovecollector reservoir 402 to dry.

Depending on the application, dried algae mass 406 is removed from net403 for further processing. Alternatively, algae mass 406 may beprocessed jointly with net 403, which becomes part of a raw material.The process of growing and harvesting algae can continue, until net 403on roll 409 is exhausted. Alternatively, net 403 may be replenished,connecting a net 403 from a new roll 409 with the end of a net 403 froman empty roll, thereby allowing continuous operating of the algaecultivation plant as shown.

An alternative harvesting technique is disclosed with reference to FIG.12. An algae cultivation pond 1200 is provided, having a recirculationinlet 1205 and a freshwater inlet 1206 on one end of algae cultivationpond 1200. On the opposite end of algae cultivation pond 1200 is anoverflow rim 1202. The top edge of overflow rim 1202 is at the lowestpoint of the wall surrounding the algae cultivation pond and therebyestablishes the maximum water level of water in algae cultivation pond1200. Overflow rim 1202 is fin-shaped, to allow algae slick 1201 toeasily flow across it. Any excess water entering algae cultivation pond1200 through recirculation inlet 1205 or freshwater inlet 1206 flowsover overflow rim 1202 into collector reservoir 1204. Disposed withincollector reservoir 1204 is conveyor belt 1203.

In a continuous operating mode of an algae cultivation plants asillustrated in FIG. 12 water constantly circulates within algaecultivation pond 1200 by pumping water through pump 1207 from collectorreservoir 1204 through pipes and recirculation inlet 1205 into algaecultivation pond 1200. Any water loss is replenished by adding waterthrough freshwater inlet 1206. Water added through freshwater inlet 1206may be rich in nutrients that are required to foster growth of algaeslick 1201. Circulation of water through algae cultivation pond 1200causes algae slick 1201 to move with the circulating water over overflowrim 1202 and onto conveyor belt 1203. Conveyor belt 1203 separates algaemass from water, and transports the algae for further processing.

In a burst operating mode, the water level in algae cultivation pond1200 is kept below overflow rim 1202 during a growth phase of algaeslick 1201. When algae slick 1201 is ready for harvest, water is addedinto algae cultivation pond 1200 through freshwater inlet 1206.Additionally, water may be caused to circulate by pumping water throughpump 1207 from collector reservoir 1204 to recirculation inlet 1205. Theflow of water from through algae cultivation pond 1200 from inlets 1205and 1206 to overflow rim 1202 causes algae slick 1201 to flow overoverflow rim 1202 onto conveyor belt 1203. Conveyor belt 1203 transportsthe algae for further processing. To provide optimal growth conditionsof algae slick 1201 water that is saturated with carbon dioxide can beinjected into the water circulation of algae cultivation pond 1200 froman underground water reservoir 1209 through pump 1208. Flue gas which isrich in carbon dioxide is inserted into underground water reservoir 1209through compressor 1210. Excess carbon dioxide which does not dissolveinto the water in underground water reservoir 1209 returns throughreturn pipe 1212 back to the flue. To protect the algae in algaecultivation pond 1200 a transparent cover 1213 is provided, whichprevents contaminants such as leafs, dust, or rain from entering algaecultivation pond 1200. Transparent cover 1213 is mounted such, that rainwater is directed into a trench 1214, which directs the rain water awayfrom algae cultivation pond 1200, thereby maintaining close control overthe environment in algae cultivation pond 1200.

An alternative algae cultivation plant is illustrated in FIG. 13. Algaecultivation pond 1300 is provided. Through water inlet 1305 water can bepumped into algae cultivation pond 1300, e.g. water that is rich innutrients that are required for algae slick 1301 to grow in algaecultivation pond 1300. Located at one end of algae cultivation pond 1300is an overflow rim 1303. Located behind overflow rim 1303 is a conveyorbelt 1304. Algae slick 1301 can be harvested manually by pulling afloating rake 1302 across algae cultivation pond 1300 towards overflowrim 1303. Floating rake 1302 pulls algae slick 1301 across overflow rim1303 onto conveyor 1304. From there, algae slick 1301 is transported byconveyor 1304 for further processing. Located around conveyor 1304 arewater drains or recirculation pipes (not illustrated) to drain waterthat is pulled with algae slick 1301 onto conveyor 1304.

An alternative approach of harvesting algae in an algae cultivation pondis the use of an algae harvesting machine 1400 as shown in FIG. 14.Algae harvesting machine 1400 is preferably used in algae cultivationponds 1420 having a width that is only slightly wider than the width ofalgae harvesting machine 1400. Algae harvesting machine 1400 comprises aframe 1402, which rests on wheels 1403. Wheels 1403 allow algaeharvesting machine 1400 to move forward and backward in algaecultivation pond 1420.

An algae slick 1401 floating in algae cultivation pond 1420 can beautomatically harvested with algae harvesting machine 1400. Algae slick1401 is picked up by a rotating harvesting barrel 1404. Harvestingbarrel 1404 comprises circumferentially and axially spaced spikes 1421which lift algae mass 1401 out of the water in algae cultivation pond1420 as algae harvesting machine 1400 moves along cultivation pond 1420.From harvesting barrel 1404 algae slick 1401 is transferred to conveyorbarrel 1405, which conveys algae mass 1401 from harvesting barrel 1404to slide 1409. Slide 1409 utilizes a comb-shaped end, through whichspikes 1406 of conveyor barrel 1405 can pass. Algae slick 1401 isseparated from conveyor barrel 1405 and slides along slide 1409 ontoconveyor belt 1410. Conveyor belt 1410 transports algae slick forfurther processing outside algae cultivation pond 1420.

Algae harvesting machine 1400 is powered electrically throughphotovoltaic cells 1411 located on top of frame 1402. Since algae slick1401 needs sun to grow, and algae harvesting machine 1400 needs sunlightto charge batteries (not shown) through photovoltaic cells 1411,photovoltaic cells 1411 can be dimensioned such, that they supply justenough energy to facilitate harvesting algae slick 1401 that has grownwhen exposed to the same sunlight as photovoltaic cells 1411.

Algae harvesting machine 1400 further comprises an exterior light sensor1407 above algae slick 1401 and a submersed light sensor 1408 belowalgae slick 1401. The difference in sunlight sensed by exterior lightsensor 1407 and submersed light sensor 1408 indicated the thickness ofalgae slick 1401, and can be used to determined the best speed of algaeharvesting machine 1400.

While the present invention has been described with reference toexemplary embodiments, it will be readily apparent to those skilled inthe art that the invention is not limited to the disclosed orillustrated embodiments but, on the contrary, is intended to covernumerous other modifications, substitutions, variations and broadequivalent arrangements that are included within the spirit and scope ofthe following claims.

What is claimed is:
 1. A construction material made of algae, comprising: a first layer of filamentous string-shaped algae having a first predominant orientation and a second layer of filamentous string-shaped algae having a second predominant orientation, wherein the first layer and the second layer are connected to each other by a binder and arranged such that the first predominant orientation and the second predominant orientation are non-parallel.
 2. The construction material as in claim 1, wherein the first predominant orientation and the second predominant orientation are about perpendicular to each other.
 3. The construction material as in claim 1, further comprising a third layer of mesh-structured filamentous algae arranged between the first layer and the second layer.
 4. The construction material as in claim 3, wherein the first layer and the second layer comprise algae of the order Zygnematales and wherein the third layer comprises algae of the order Chlorococcales.
 5. The construction material as in claim 1, further comprising an additive of silicic acid or diatom algae particles.
 6. The construction material as in claim 1, wherein the first layer of filamentous string-shaped algae and the second layer of filamentous string-shaped algae comprise pyrolyzed filamentous algae.
 7. A method for producing for a construction material made of algae, comprising: harvesting algae; drying the algae to form a dried algae mass; placing the dried algae mass into a sealed container, the algae mass being held by mounting fixtures at both ends of the sealed container; holding the algae mass under tension by the mounting fixtures; heating and evacuating the sealed container; allowing the algae mass to carbonize; and removing carbonized algae material from the container.
 8. The method as in claim 7 wherein heating the sealed container occurs in several steps, between 600° C. and 900° C.
 9. The method as in claim 7 wherein the dried algae mass comprises cells having a predominant orientation and wherein the dried algae mass is placed into the container such that its cells are predominantly oriented parallel to the tension created by the mounting fixture, thereby causing a predominant orientation of carbon fibers in the carbonized algae material.
 10. The method as in claim 9, further comprising: soaking two mats of carbonized algae material in a binding agent and placing the two mats onto each other such that the predominant orientation of carbon fibers in each mat is substantially perpendicular to each other. 